1. Field of the Invention
The present invention relates to a display screen control apparatus for controlling an image on a display unit by operating a single operation lever and suitably applicable to, for example, a navigation system mounted on a vehicle, copy machine and the like.
2. Description of the Related Art
A conventionally known example a screen display control apparatus of the type is arranged such that 4 sets of push switches mounted on a printed circuit board at the same intervals of 90.degree. is covered with an upper case, an operation lever is oscillatingly supported at the central position of the group of these push switches serving as a fulcrum and the position of a cursor, and the like on a display unit is controlled based on the turned-on signal of the push switch or switches selectively urged and driven by the operation lever. More specifically, in the conventional example, when an operator tilts the shaft portion of the operation lever extending to the outside of the housing composed of the combination of the printed circuit board and upper case, the one or two sets of push switches disposed in the direction toward which the shaft portion is tilted are urged and driven by the operation lever, and thus an image or cursor on the display unit can be moved in a desired direction by operating the single operation lever so that the screen display control apparatus can be conveniently used for, for example, the movement of a map in a navigation system, movement of a cursor in a personal computer, and the like.
Nevertheless, since the aforesaid conventional screen display control apparatus only selects a control signal by the direction in which the operation lever is tilted, when a different kind of functions are to be controlled, for example, when a map in a navigation system is to be enlarged or reduced, an operation member other than the operation lever must be operated. Since the operation lever must be spaced apart from the other operation member to a certain extent due to the restriction resulting from an operating space and design, however, an operator must move his or her hand and fingers in a large amount in a complicated manner to continuously control a plurality of kinds of functions, and thus a problem arises in that operability is extremely lowered. Note, this problem is not limited to the navigation system but also caused in personal computers and the like employing the conventional display screen control apparatus in the same way and, for example, in the case of the personal computers, an operation member for feeding a page and establishing set conditions is need in addition to the operation lever for moving a cursor.
An object of the present invention made by taking the problem of the aforesaid prior art into consideration is to provide a display screen control apparatus capable of controlling a plurality of kinds of functions by operating a single lever and excellent in operability.